This invention relates to the field of fastenings made by nuts and threaded shafts. More specifically, the invention comprises a device which covers and protects a nut and exposed portion of a threaded shaft from corrosion found in harsh environmentsxe2x80x94such as saltwater immersion. The device substantially inhibits rusting of the nut itself and the exposed portion of the threaded shaft extending beyond the nut, allowing the nut to be easily removed even after it has been left in place for some time.
Lug nut protective device are well known in the prior art. Many of these protective devices are theft deterrents. One such invention is disclosed in U.S. Pat. No. 4,521,146 to Wharton (1985). The Wharton patent discloses a wheel nut cover having threads which strip upon tightening to create a tamper-resistant assembly. A similar device is disclosed in U.S. Pat. No. 4,786,224 to Wharton (1988). The ""224 device includes a protective shroud which fractures upon tightening, creating a similar tamper-resistant assembly.
A device having similar objectives is disclosed in U.S. Pat. No. 4,824,305 to McCauley (1989). The McCauley device actually substitutes a different type of lug nut for the standard type found on most automobile and trailer wheels. The lug nut has an internal cavity in a special shape configured to receive a special type of removing tool. Without the tool, it is very difficult to remove the lug nut.
A simpler type of device is disclosed in U.S. Pat. No. 4,890,967 to Rosenbaum (1990). The Rosenbaum device is not primarily concerned with theft deterrence. Instead, its focus is to protect the lug stud and lug nut from corrosion. It attempts to accomplish this via covering the lug bolt""s exposed surfaces (although the Rosenbaum disclosure illustrates a lug bolt, it appears to be equally applicable to the more common arrangement of a lug stud and lug nut). While somewhat effective for warding off salt sprays and other corrosive environments, the ""967 device provides no positive seal to prevent water leaking into the cover upon immersion. As will be explained subsequently, water immersion is a significant concern.
U.S. Pat. No. 5,380,070 (1995) discloses a domed plastic lug nut cover. Its stated purpose is to allow the securing of a wheel cover (xe2x80x9chub capxe2x80x9d) to a wheel without removing the lug nuts. The device actually threads onto the exposed portion of a lug stud. Of course, since many lug studs do not have threads extending past the lug nut, the ""070 device will not work in many applications. In addition, like the Rosenbaum device, the ""070 device has no positive seal to prevent water leaking into the cover upon immersion.
U.S. Pat. No. 5,810,532 to Huang (1998) discloses another domed plastic lug nut cover. This particular device uses pliable spring clips to secure itself to a lug nut. While potentially effective for one size of lug nut, different size clips would be required to accommodate the wide variety of lug nuts presently on the market. In addition, the Huang device also lacks any type of positive seal to prevent water penetration.
Another domed plastic cover is disclosed in U.S. Pat. No. 5,857,818 to Bias (1999). This device uses the pliable nature of the material itself to frictionally engage and hold itself to the hexagonal side walls of a lug nut. Obviously, the device must be sized to fit a particular lug nut, raising the same concerns as seen for the Huang device. It also lacks any type of water seal.
The lack of a water seal is a significant concern, especially where the device is to be used on boat trailer lug nuts. The lug nuts on boat trailers are always immersed completely in water when launching and retrieving a boat. If water is able to invade a protective lug nut covering, it will often remain trapped there for several hours. This phenomenon causes significant corrosion, especially when the lug nut has been immersed in salt water.
In addition, the protection of a nut locked on a threaded shaft obviously has applications far beyond the automotive industry. Many coastal installations have nuts and threaded shafts exposed to a salt air environment. These typically become rusted and inoperable in a matter of months. Accordingly, the protection of a nut locked on a threaded shaft is a desirable objective.
The known devices for accomplishing this goal are limited in that they:
1. Must be particularly adapted to fit a specific nut;
2. Must be able to thread onto an exposed portion of the threaded shaft;
3. Require the use of springs or specialized tools to lock them in place; and
4. Do not effectively protect against corrosion, especially following water immersion.
Accordingly, several objects and advantages of the present invention are to provide a protective nut cover which:
1. Will accommodate a wide variety of nuts and shafts;
2. Does not require an exposed portion of thread to be held in place;
3. Does not require the use of springs or specialized tools to be locked in place; and
4. Effectively protects against corrosion, especially following water immersion.